Power calculations of the upcoming study is based upon a previous studies by Grossman et. al.(3) MK in THA at Baseline: 35 mTBI subjects (mean 0.74, sd 0.08), 35 healthy controls (mean 0.89, sd 0.04), power = 100% MK in THA at Follow up: 25 mTBI (mean 0.78, sd 0.06), 25 healthy controls (mean 0.89, sd 0.12) power = 96% An ANOVA will be used to test the difference in signal to the two times (<14 days and 3 months after mTBI).